1. Field of the Invention
This invention relates generally to coupling sectional rods into one continuous rod, and more specifically to coupling sectional rods into one long continuous rod for use in clearing obstructions in sewers or underground pipes.
2. Brief Description of the Prior Art
Several different types of coupling means for flexible rods or shafts used in "rodding" or clearing obstructed underground pipes or drains are known in the the art. Such rods can be on the order of hundreds of feet long and are coupled end-to-end to provide a total length far exceeding the length of any single rod. These rods must be joined such that torsional forces applied to one end of a first rod in a coupled set of rods will be transmitted through the rod length to the last rod.
Typically, in clearing an obstruction, an assembly of coupled rods is forced down through an underground pipe or drain with rotation of the assembly. More rods are added as the coupled rod assembly is forced through the pipe.
The coupled rod assembly, being flexible, can wind its way through the convolutions of the sewer pipe. It is forced through obstructions and loosens debris in the pipe. The obstructions and debris are later washed through the pipe.
In order to make the coupled rod more efficient at clearing obstructions, a suitable tool, such as a drill, a centrifugal cutter or a root saw, is connected at the leading end of the coupled rod assembly. At the opposite end rotary torsion is applied to the coupled rod assembly. This torsion is transmitted along the length of the rod, through each coupling to the next rod until it ultimately is applied to the end of the last rod. The torsional force applied to the tool at the end of the last rod drills through the obstruction cleaning the sewer pipe.
In addition to being a suitable means for clearing sewer pipes, such coupled rod assemblies are suitable for applying torsional forces to many otherwise inaccessible, remote areas. This permits use of drills, centrifugal cutters or root saws in places where ordinary access would not be allowed.
Such coupled rod arrangements are also suitable for fitting rods through convoluted tubes or passageways. It is used to `snake` wires through passageways for wiring houses or running telephone line.
U.S. Pat. No. 2,319,892 ("Thomas") shows a means for coupling rods or shafts. An eyelet is shown on the end of a first rod and a corresponding hook on the end of a second rod. The hook fits through the eyelet. A threaded cap surrounds the shaft and near the hook and a capsule having a receiving thread fits around the eyelet. When the hook engages the eyelet the capsule is in proximity of the threaded cap which threads into the capsule. The cap and capsule enclose the hook and eyelet. As torsion is applied to one of the rods, for example, the rod having the hook at its end, the torsional force causes the rod having the eyelet to rotate. The geometry of the hook-eyelet connection allows a degree of rotational play.
U.S. Pat. No. 2,168,759 ("Betzing") discloses a rod coupling device. It employs a capsule and threaded cap similar to Thomas. In Betzing's device there is a pin in the capsule which is perpendicular to the length of the rod. Each rod ends in a semicircular hook. These hooks fit over and catch the cross-pin in the capsule. When both hooks catch the cross-pin the capsule, the cap is then threaded into the capsule enclosing both hooks in the cross-pin. The torsional forces applied to the first rod allow the rod to twist slightly before engaging the cross-pin which rotates the second rod. The slight amount of roll of the rod on the cross-pin allowed in the coupling gives a degree of rotational play.
U.S. Pat. Nos. 3,779,658 ("'658 patent"), U.S. Pat. No. 3,814,529 ("'529"), U.S. Pat. No. 3,873,223 ("'223") all relate to coupling means for joining rod ends. All employ a capsule and screw cap arrangement which encloses flattened ends of the rods to be joined. The capsule of the '223 and the '529 patents employ a three-piece structure comprising two caps in the central capsule section which the caps thread into. Both the '529 and the '223 patents employ a single type of connecting end. This allows any end of a rod to be connected to any other end. The '658 patent employs two differing ends which must be matched together. Since the ends of the rods of the '223, the '658, and the '529 patents employ a flattened design, and the capsules are radially symmetric, there is an intervening space between the capsule and the flattened ends.